/Engine/Plugins/FX/Niagara/Source/NiagaraEditor/Public/NiagaraEditorData.h
Find a script variable with the same key as RemovedScriptVarId and unmark it as being sourced from a parameter definitions.
bool SynchronizeParameterDefinitionsScriptVariableRemoved ( const [FGuid](API\Runtime\Core\Misc\FGuid) & RemovedScriptVarId )